Moulding plastic material



gmwnwm A a L' Oct. 20, 1959 B. BRUNTON uoummc PLASTIC MATERIAL Filed March 9, 1955 Befl/zard Brunto/z ATTORNEYS United States Patent The present invention relates to the production of moulded articles produced from wood wool and like vegetable material.

The invention is more particularly though not exclusively concerned with the manufacture of what is known as wood wool slab and panels incorporating wood wool as part or whole of the core. The invention is concerned with the moulding and rigidifying of wood wool and other like vegetable material in conjunction with cement.

For the purposes of the invention cement means a powdered, hydraulically settable material that, made plastic with aqueous medium such as water, hardens on drying.

In prior patent No. 2,394,146 there is described a method of making a building panel in which wood wool bound with cement forms the core. This prior patent describes the preparation of the wood wool prior to moulding and includes the step of soaking or saturating the wood wool in a cement slurry.

An object of the present invention is to provide an improved method of preparation for the wood wool or other vegetable material prior to its introduction into the mould whereby better control is obtained and a more accurate and consistent product produced as a result.

Broadly, the invention com rises a methpd forproducmg mcifilded articles ffom wood wool and like vegetablema'terial which 'ificlude's' the's'teps ofjirst wetting the wood woolor like vegetable material with that amount of'aqueous medium which is naturally retained on the surface thereof and preferably without materially increasing its internal moisture content and maeartermzrwhnsrrh aiiieiiusg edifim'rsmniremneu oTflresu'rfacoftlie'wood wool or like vegetable mate rialfadding tothewetted wood wool or other vegetable materialwhilst 'in a state of continuous agitation dry powdered, hydraulically settable cement to form in situ a continuous coating of cement slurry upon the surface of the wood wool or like vegetable material and subsequently moulding the resultant mixture of wood wool and cement slurry.

A further feature of the invention is the pre-treatment of the wood wool or other vegetable material to control the subsequent setting and curing of the cement. It has been found that with some grades ofwood wool the resinous or sap moisture content is such that in a temperate climate the setting of the cement is inhibited or permanently prevented unless the wood wool is pretreated with an inhibitor for inhibiting the retarding 2,909,439 Ce Patented Oct. 20, 1959 Whilst the dry powdered cement is being added the wood wool is subjected to continuous agitation and it is preferred to submit it to a uni-directional agitation of such a nature that it is not merely tumbled but is lifted and teased during the agitation at such a speed as to ensure a rapid dispersion of the powdered cement throughout the body of the wood wool.

By way of example and using wood wool as the vegetable material the wood wool which is normally delivered in bales is teased out into loose form and weighed into batches suitable to the capacity of the mixing machine referred to hereinafter. Each batch of wood wool is then immersed in an aqueous medium which for a temperate climate comprises an approximately 10% by weight solution of calcium chloride in water. This immersion is of such short duration as to prevent any substantial absorption of the water into the wood but of suflicient duration to allow a thorough wetting of the surface of the wood wool. Normally, it is found that an immersion should not be longer than 7-8 minutes. After immersion the wood wool is allowed to drain so as to lose the water which is not held naturally upon the surface of the wood wool.

The wood wool is then transferred before any substantial loss by evafiii'atidri *ar waermirrfie "a mixing machine whicucornprises a drum containing rotary tines action of the resin or sap moisture or an accelerator for the setting of the cement. calcium chloride.

and in which the is submitted to continuous unidirectional agitation and teasing. Into this drum and whilst the wood wool is being agitated there is added in di'y 3owdered form a rapid hardening cement in an appgggimate proportionof three parts of cement by weight to on'pai-t'of dry wood wool. In the mixer the cement rapidly becomes dispersed evenly throughout the wood wool and combines with the water held upon the surface of the wood wool to form a continuous cement slurry coating upon the surface of the wood wool. Under normal circumstances the period of mixing is of the order of 30 seconds.

The mixture of wood wool and cement slurry so formed is then removed from the mixing machine and introduced into suitable moulds where it is allowed to set and cure preferably under pressure in known manner.

The aqueous wetting medium containing, if desired, a suitable accelerator or inhibitor is conveniently contained in a large tank into which the wood wool is dipped manually for example by means of forks and the strength of the solution if an inhibitor or accelerator is employed may be maintained by periodically topping up with-a solution of similar strength. Periodical checks of the strength of the topped up bath may be made by the use of an hydrometer.

Alternatively, the 'wood wool may be dipped mechanically and for example each weighed batch may be conture content of the wood wool should be maintained below 30% and more particularly when wood wool slab or building panels having a core of wood wool are being manufactured the fibres of the wood wool are preferably of the order of 10" or more in length, the thickness being of the order of 0.200.30 mm. and the width being of the order of 1.5-2.5 mm.

In the sole figure of the accompanying drawing there is shown diagrammatically one form of installation suitable for carrying the invention into efiect.

As will be seen from the drawing, the installation comprises a preparation platform 1 on which wood wool, delivered thereto in bales, is teased out into loose form and weighed into batches suitable to the capacity of a mixing machine 2 hereinafter referred to in greater detail. Adjacent one end of the platform 1 is a tank 3 for containing an aqueous medium 8 comprising for example an approximately 10% by weight solution of calcium chloride, and containing if desired a suitable accelerator or inhibitor.

The weighed batch of dry wood wool is dipped manually, for example, by means of forks, into the aqueous medium for a short time suflicient to allow a thorough wetting of the surface of the wood wool but insufiicient for the wood wool to absorb any substantial amount of liquid. The wood wool is then placed on a draining platform 4 formed of a plurality of laths 5 secured together in spaced relation by cross battens 6, and allowed to drain so as to lose. any liquid which is not held naturally upon the surface of the wood wool. The drained liquid is collected in a receptacle 7 supported beneath the draining platform 4.

The mixer 2 is disposed at the end of the draining platform 4 distant from the tank 3 and comprises a hollow body 9 through which extends a rotatable shaft 10 having secured thereto within the body tines 10a. The bottom of the body 9 is provided with a discharge aperture closed by a hinged flap 11 connected by pivoted links 12 and 13 to a handle 14 pivoted on a cross shaft 15 so that by raising the handle from the position shown in the drawing, the flap 11 hinges downwardly to open the discharge aperture of the body 9. The upper part of the body is open as at 16 adjacent the end of the draining platform 4 to facilitate the loading of wood wool from the draining platform into the mixer.

The batch of wetted wood wool on the draining platform 4 is transferred after the excess liquid has drained from the wood wool but before any substantial loss by evaporation occurs, into the mixer 2 and is submitted to continuous unidirectional agitation and teasing by the tines secured to and rotating with the shaft 10. Whilst the wood wool is being agitated in the mixer, a rapid hardening, hydraulically settable cement in dry powdered form is added in an approximate proportion of three parts of cement by weight to one part of dry wood wool. The mixing is continued until the cement becomes evenly dispersed throughout the wood wool and combines with the liquid held on the surface of the wood wool to form a continuous cement slurry coating thereon. Under normal circumstances the period of mixing is of the order of 30 seconds.

The handle 14 is then raised to open the flap 11 and the wood wool-cement slurry mixture is discharged from the mixer into suitable receptacles for conveying it to the moulds, or it may if the size of the mould is suitable, be discharged directly into the mould. Afterthe mixed wood wool and cement slurry has been accom-H mfodated in'the mould or moulds, it is allowed to set and cure preferably under pressure in known manner.

What I claim is:

1. A method oj producing moulded articles from wood 0 m a moisture content of less than 30% which comprises teasing the wood wool into loose form, weighing ;the "wood wool into batches "of a'predetermined weight, immersing each batch in water for a period of less than eight minutes to allow a thorough wetting of surface of the wood wool with the moisture content of the wood wool being maintained below 30% to preserve the fibrous and cellular structure of said wood wool, dra ininiz the batch so as to lose apy liggid whjch is not held naturally uponthe surfaceofthe wool, introducing thJdi'aiHdwood wool, before any substanti al loss or moisture takes place due to evaporation, into a and submitting the wood woo1 to a continuous unidirectional agitation and teasing for a period of approximately thirty seconds, adding powdered, hydraulicall settable cement to the wood wool while the wool is agitated so that the cement combines with the liquid on the surface of the wood wool to form in situ a continuous cement slurry coating upon the surface thereof, discharging the wood wool having the cement slurry mixtuTfher'eoi -fgom the mixer and into moulds to form the article, and allawm rm st and cure.

T'Ilfe'method according to claim 1 wherein there is dissolved in the water approximately 10% by weight of calcium chloride.

3. The method according to claim 1 wherein the cement is added to the wood wool in approximate proportions of three parts by weight of cement to one part by weight of dry wood wool.

4. The method according to claim 1 wherein the fibers of the wood wool are selected to have a minimum length of the order of 10", a thickness of from 0.20 to 0.30 mm. and a width of from 1.5 to 2.5 mm.

5. A method for producing moulded articles from wood wool having a moisture content of less than 30% which includes the steps of wetting only the outer surface of the wood wool with an amount of water so that the internal moisture content of the said wood wool is maintained at less than 30%, preserving the fibrous and cellular structure of said wood wool, retaining moisture on said outer surface of said wood wool, adding a predetermined quantity of dry powdered, hydraulically settable cement to the wetted wool while in a state of continuous agitation forming a continuous coating of cement slurry in situ upon the surface of the wood wool, said agitation being unidirectional and existing for a period of approximately thirty seconds whereby the wood wool is lifted and teased at such speed that the powdered cement is rapidly dispersed through the mass of wood wool, and subsequently moulding the mixture of cement slurry and wood wool.

References Cited in the file of this patent UNITED STATES PATENTS 1,618,512 Christiansen Feb. 22, 1927 2,175,568 Haustein Oct. 10, 1939 2,394,146 Brunton et a1. Feb. 5, 1946 2,504,579 Perl Apr. 18, 1950 

1. A METHOD OF PRODUCING MOULDED ARTICLES FROM WOOD WOOL HAVING A MOISTURE CONTENT OF LESS OF 30% WHICH COMPRISES TEASING THE WOOD WOOL INTO LOOSE FORM, WEIGHING THE WOOD WOOL INTO BATCHES OF A PREDETERMINED WEIGHT, IMMERSING EACH BATCH IN WATER FOR A PERIOD OF LESS THAN EIGHT MINUTES TO ALLOW A THOROUGH WETTING OF THE SURFACE OF THE WOOD WOOL WITH THE MOISTURE CONTENT OF THE WOOD WOOL BEING MAINTAINED BELOW 30% TO PRESERVE THE FIBROUS AND CELLULAR STRUCTURE OF SAID WOOD WOOL, DRAINING THE BATCH SO AS TO LOSE ANY LIQUID WHICH IS NOT HELD NATURALLY UPON THE SURFACE OF THE WOOD WOOL, INTRODUCING THE DRAINED WOOD WOOL, BEFORE ANY SUBSTANTIAL LOSS OF MOISTURE TAKES PLACE DUE TO EVAPORATION, INTO A MIXER AND SUBMITTING THE WOOD WOOL TO A CONTINUOUS UNIDIRECTIONAL AGITATION AND TEASING FOR A PERIOD OF APPROXIMATELY THIRTY SECONDS, ADDING POWDERED, HYDRAULICALLY-SETTABLE CEMENT TO THE WOOD WOOL WHILE THE WOOL IS AGITATED SO THAT THE CEMENT COMBINES WITH THE LIQUID ON THE SURFACE OF THE WOOD WOOL TO FORM IN SITU A CONTINUOUS CEMENT SLURRY COATING UPON THE SURFACE THEREOF, DISCHANGING THE WOOD WOOL HAVING THE CEMENT SLURRY MIXTURE THEREON FROM THE MIXER AND INTO MOULDS TO FORM THE ARTICLE, AND ALLOWING IT TO SET AND CURE. 